Override cluster symbol
This sample demonstrates how to override the default cluster symbol when point clustering is enabled on a GeoJSONLayer. Clustering is a method of reducing points in a FeatureLayer, CSVLayer, GeoJSONLayer, WFSLayer, or OGCFeatureLayer by grouping them based on their spatial proximity to one another. Typically, clusters are proportionally sized based on the number of features within each cluster.
Clustering is configured in the featureReduction property of the layer. The feature reduction property gives you control over many cluster properties, including the cluster symbol. This allows you to retain the layer's renderer for styling individual features, but visually indicate clusters with a dedicated symbol.
Related samples and resources

Point clustering - basic configuration
Point clustering - basic configuration

Point clustering - filter popup features
This sample demonstrates how to filter clustered features within a cluster's popup.

Point clustering - generate suggested configuration
Point clustering - generate suggested configuration

Point clustering - query clusters
Point clustering - query clusters

Point clustering - advanced configuration
Point clustering - advanced configuration

Popup charts for point clusters
This sample demonstrates how to summarize clustered features using charts within a cluster's popup.

Point clustering with visual variables
Point clustering with visual variables
FeatureReductionCluster
Read the API Reference for more information.